The present invention relates to an antenna device comprising feeding means and an hand-held mobile communication device comprising such an antenna, in general, and more specifically to an antenna device comprising feeding means and an hand-held mobile communication device comprising such an antenna for receiving and transmitting circular polarized RF signals for communication via satellites.
Hand-held satellite communication devices, using satellites as a first link in the communication, is being increasingly popular and fulfills a demand for communication in unpopulated areas where ordinary cellular type of mobile communication is not possible due to, for instance, economy.
Hand-held satellite communication devices uses circular polarized RF signals for communication with the satellite since it is not possible to know how the satellite is oriented in space. The use of circular polarized RF signals puts somewhat different requirements on the antennas for such devices as compared with ordinary cellular antennas. A commonly used solution uses a quadrofilar antenna comprising four helical radiating elements coaxially arranged and coextending, each fed with 90xc2x0 phase difference. The antenna is contained in a cylindrical housing. For optimal performance it is also common to have some sort of matching means between the antenna and the hand-held mobile communication device.
When a manufacturer of hand-held mobile communication devices assembles a device, it is of course important that the assembly is as smooth as possible and the number of steps in the assembly is as few as possible. This is advantageously since each step, by itself, introduces a possible fault in the process. It is a desired feature of assembly processes to have a block structure where several building blocks is assembled and tested separately to find faulty building blocks and that the building blocks then are assembled into bigger building blocks to finally be assembled to the complete product. In the assembly process the antenna is one such part that will be assembled onto the hand-held device and connected to the circuitry of the hand-held device.
It is desired that the number of steps for assembling the antenna device onto the hand-held mobile communication device is kept low. For a quadrofilar helical antenna device QHA, as described above, the number of radiating elements to be connected are four, and it would of course be advantageously if this could be reduced. The more general NHA denotes a N-filar helical antenna where N is the number of radiating elements and is greater than one.
If the hand-held mobile communication device is required to receive and/or transmit in two frequency bands with a relatively large separation the common solution has been to use two different antennas tuned to each separate frequency. This results in eight wires to connect from the radiating elements to the circuitry of the hand-held communication device.
A such antenna is disclosed in the French application FR-2746548, by France Telecom, where a dual band antenna is disclosed having two independent quadrifilar helical antenna elements. Each of these antenna elements operate in a specific frequency band and have separate phasing networks. Each antenna element is manufactured on a flexible substrate which is mounted on a cylindrical substrate, a first on the inside and a second on the outside. The construction of this antenna is complicated, require two antenna elements, and is expensive to manufacture, and furthermore have an unwanted high height.
If only one antenna is to be used it is required to use specific circuits in the hand-held mobile communication device which is selected according to the specific characteristics of the selected- antenna. It is of course a problem for an independent manufacturer of hand-held communication devices if it is necessary to add specific circuitry in dependence of the antenna supplier currently selected.
It would thus be an advantage if the interface between the hand-held device and the antenna could be made simple.
The PCT patent application, WO 97/11507 by Quallcom shows a feeding network on a feed portion of a substrate that provides phased signals to the radiators. This solution will have a generally larger size, and thus larger antenna, than if discrete components are used. It is also very difficult to add discrete components to a flexible substrate, which is formed to a cylindrical shape.
U.S. Pat. No. 5,628,057 assigned to Motorola describes a self-phased antenna with external transformation network. The transformation network supplies phased signals to the radiating antenna as a separate entity. The use of delays in cables makes the antenna somewhat narrow in operative frequency band which might be functional for some applications but will constitute problems for applications where two frequency bands are required or where a broader frequency band is needed. The specific solution does not allow for any extra components in the antenna.
The following patent applications are related to the same tecnical field as the invention of this application, and are hereby incorporated herein by reference:
the Swedish patent application SE 9801754-4 having the title xe2x80x9cAn antenna system and a radio communication device including an antenna systemxe2x80x9d, filed in Sweden the same day as this application, May 18, 1998, applicant Allgon AB,
the Swedish patent application SE 9801755-1 having the title xe2x80x9cAntenna device comprising capacitively coupled radiating elements and a hand held radio communication device for such antenna devicexe2x80x9d, filed in Sweden the same day as this application, May 18 1998, applicant Allgon AB, and
the Swedish patent application SE 9704938-1, filed Dec. 30, 1997, applicant Allgon AB, having the title xe2x80x9cAntenna system for circularly polarized radio waves including antenna means and interface network.xe2x80x9d
The object of the present invention is thus to achieve an easily mounted antenna device for receiving and/or transmitting circular polarized RF signals in at least one and preferably two frequency bands with a well defined interface towards the circuitry in the hand-held mobile communication device.
The problems described above, how to achieve an easily mounted NHA (N-filar helical antenna, N greater than 1) antenna device for receiving and/or transmitting circular polarized RF signals in at least one, preferably two different frequency bands, is solved by providing N radiating elements where N is an integer greater than one, a support means arranged to support said radiating elements, and at least one connection member arranged to be easily connectable to a circuitry arranged on a first printed circuit carrier arranged in said hand-held mobile communication device. Further more, providing at least one phasing network comprising N first ports arranged to be connected to said radiating elements and at least one second port arranged to be connected to said connection member, said phasing network being mounted to said support.
In more detail the objects of the present invention, with how to achieve an easily mounted antenna device with a simple and well defined interface are obtained, according to one embodiment, by providing, in addition to the above, a support which is mainly cylindrical, a second printed circuit carrier which is securely mounted on said support with the normal of said second printed circuit carrier parallel to the axis of said mainly cylindrical support and the radius of a circle circumscribing said printed circuit carrier being not larger than the radius of said mainly cylindrical support, said second printed circuit carrier being connected to said N radiating elements on one side, a third printed circuit carrier securely mounted on said second printed circuit carrier with its normal perpendicular to the normal of said second printed circuit carrier and in one end connected to said at least one connection member.
Said phasing network is arranged on said third printed circuit carrier and said first and second printed circuit carrier connects said connecting member with said N radiating elements through said phasing network.
Said antenna device further comprises a diplexer arranged for transceiving RF signals from said phasing network, diplexing said RF signals into at least a first Tx frequency and at least a first Rx frequency, and transceiving said at least first Tx and at least first Rx frequencies to a first and a second connection member, and wherein said diplexer being arranged on said third printed circuit carrier and substantially enclosed in said housing.
In more detail the objects of the present invention, with how to achieve an easily mounted antenna device with a simple and well defined interface are obtained, according to another embodiment, by providing, an antenna device which further comprises N diplexers arranged for transceiving RF signals from said N radiating elements, diplexing said RF signals into at least a first Tx frequency and at least a first Rx frequency, transceiving said at least first Tx frequency to a first phasing network, transceiving said at least first Rx frequency to a second phasing network, said first phasing network being connected to a first connection member and said second phasing network being connected to a second connection member, and where said diplexer being mounted to said support and substantially enclosed in said housing.
An advantage with the present invention is that an easily mounted antenna for receiving and/or transmitting circular polarized RF signals in at least one, preferably two or more, relatively separate frequency bands, well designed for manufacturing processes is achieved with a well defined interface towards the circuitry in the hand-held communication device. Such an antenna is well suited for mass production.
An advantage, according to one embodiment of the invention, is that only one antenna is needed for receiving and/or transmitting circular polarized RF signals in two relatively separate frequency bands.
Yet another advantage with the present invention is that since the diplexer is arranged in the antenna device, a LNA (Low Noise Amplifier) may also be arranged in the receiving branch in the antenna device since the relative strong transmission signals is separated from the relative weak received signals. Thus the signals received by the antenna can be amplified before the signals is transmitted from the antenna to the tranceiving circuitry and damping occurring in the connection members between the antenna and the tranceiving circuitry can be made less disturbing.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.